This subproject is focused on the organization of glomerular inputs to the piriform cortex and the intracortical circuitry that is related to the glomerular inputs. The studies use an in vitro slice preparation, developed by the investigators, that includes, intact, the OB in connection with the PC. The preparation contains intracortical connections and centrifugal PC to OB connections as well. There are two aims. Aim 1 is to test the hypothesis that mitral/tufted cells whose dendrites coalesce in an individual glomerulus have axons that terminate with topographic specificity in the PC. This will be accomplished with focal glomerular applications of anterograde anatomical tracers and with field potential and voltage sensitive dye techniques. to determine whether circuits within the PC form topographically arranged functional units, and whether the patterns of those units are related to patterns of afferent inputs from the glomeruli. This aim utilizes coordinated tract-tracing and functional (field potential, voltage sensitive dye) approaches. Neuronal recording in the PC will determine how synaptic interactions between glomerular inputs zones are organized in the PC. Intracellular staining will map axon collaterals from recorded cortical cells in relation to glomerular inputs zones optically imaged in the same experiment. The overall goal is the elucidation of the circuit diagram involving PC pyramidal cells, glomerular input zones, and intracortical pyramidal axon connections. Physical resources, space and equipment are all adequate for the performance of this subproject.